The present invention relates to a shop-floor programming (SFP) system for a STEP-NC controller and a method for generating a part program for use in the STEP-NC controller by using an ISO 14649 data model.
A shop-floor programming (SFP) system refers to a system including all essential functions required to create and verify a part program on a computer-based numerical control (CNC) apparatus. By using such a SFP system, functions of a CAD/CAM system, which is operated independently of the CNC system in an off-line condition, can be performed at a shop-floor. Conventionally, there has been developed by several CNC manufacturers a SFP system capable of producing a part program through the use of G codes in accordance with ISO 6983. However, such a SFP system has been implemented as an interactive SFP system that can be applied to a numerical control apparatus of only the manufacturers who developed that system. As such SFP systems, there exist, for example, Blue-print/Support programming and WOP system of Siemens, Super-CAP system of FANUC, an interactive programming system of MAZAK, Compact programming system of YASNAC, etc.
The above-mentioned ISO 6983 is widely used as a standard of data interface for a Numerical Control (NC) apparatus in a manufacturing process. However, the ISO 6983 is a low-level international standard that just defines an axis movement command (G-code) and a switching command (M-code). Thus, with these low level commands, a post-processor should produce a part program having a tremendously large size, wherein maintenance and decoding of the produced part program is very difficult. Furthermore, since the ISO 6983 only supports linear and circular movements, a geometry having a more complicated form, e.g., a spline, cannot be produced by using the ISO 6983 standard. Several CNC manufacturers attempt to solve this problem by adding to the ISO 6983 standard high-level commands of their own. However, since each of the manufacturers has their own standard, compatibility of the part programs is reduced. In addition, since the SFP system using the G-codes according to the ISO 6983 standard is manually operated by using the G-code and the M-code, various production information such as machining features, a machining process, a machining technology, cutting tools, machining knowledge and feature information may not be included in the part program.
As a solution to the above-mentioned drawbacks of the ISO 6983, ISO 14649 standard has been introduced. The ISO 14649 defines a method for incorporating a variety of production information in a new type part program that is different from the prior one using the G-codes. The ISO 14649, which is instituted to define an interface for use in information exchange between a CAD/CAM system and CNCs, accepts the definition of STEP (Standard for the Exchange of Product Model) as it is or more specifies the definition to make it more adequate for the CNC. Accordingly, a system adopting the ISO 14649 standard exhibits a highly improved compatibility with up-coming data and other systems. Further, the system according to ISO 14649 standard can utilize information generated at a CAD/CAM system where the STEP is currently employed as an exchange information model. Still further, a part program in the system according to the ISO 14649 can be easily modified and becomes to have a systematic and hierarchical interface grammar.
In the meanwhile, the part program created by using the conventional G-codes according to IS 6983 is either directly produced by a manufacturing engineer or modified by a machinist after being produced at an off line CAM system. Alternatively, the part program is created by an interactive programming system included in a CNC controller. Accordingly, a part program for manufacturing a comparatively simple geometry, not a complicated one, is created and modified by an expert machinist in a manual mode.
However, the part program for use in the STEP-NC (STEP-Compliant Data Interface for Numerical Controls) in accordance with the ISO 14649 should contain therein a variety of production information such as machining features, a machining process, a machining method, cutting tools, machining technology and geometry information. Moreover, the part program should describe exact parameters for defining the above-cited various production information. That is, it is difficult for even an expert machinist to create or modify a part program in accordance with the ISO 14649 for the purpose of manufacturing just a simple feature as well as a complicated one, which is quite different from a case of a part program generated according to G-codes.
Therefore, there has been intensified a demand for a technique capable of automatically producing a part program for use in the STEP-NC.
It is, therefore, an object of the present invention to provide a method for automatically producing a part program for use in a STEP-NC and CNC internal data by using CAD data generated according to STEP.
In accordance with the present invention, there is provided a method for automatically generating a part program for a STEP-NC (STEP-Compliant Data Interface for Numerical Controls) in a SFP (shop-floor programming) system based on an ISO 14649 data model, the method comprising the steps of: (a) generating geometric kernel data by interpreting a STEP physical file or an ISO 14649 part program; (b) recognizing manufacturing features from the geometric kernel data; (c) setting a process plan according to the ISO 14649 on the basis of the manufacturing features; (d) editing the process plan; (e) generating an ISO 14649 part program from the edited process plan; (f) generating a tool path based on manufacturing feature information specified in the ISO 14649 part program; and (e) verifying the produced tool path in a CNC (computer-based numerical control) apparatus.